This invention relates to the field of electrodes for automatic analytical chemical instruments. More particularly, the invention is concerned with a salt bridge in flow cells of analytical instruments.
Flow cell analyzers operate with a combined mixture of diluent and fluid sample flow past various electrodes for the determination of electrolytes in the fluid sample. Usually four electrolytes, namely, sodium, potassium, chloride and CO.sub.2 are determined in the flow cell. It is often desirable to connect different flow paths together without introducing new potential to the electrodes. The salt bridge provides a non-flow or very low flow path between these different flow paths and in effect a conductivity path.
In the prior art, salt bridges are relatively permanently located in a flow cell, and have drawbacks in that they are difficult to align and assemble relative to the flow cell and different flow streams. The alignment of the salt bridge is particularly critical. It is thus difficult to set the salt bridge effectively and accurately in the flow cell. Additionally, when maintenance is necessary and the salt bridge needs to be removed from the flow cell, it is necessary to disassemble the entire flow cell. Difficulties also arise in the creation of air bubbles in adjacency with elements of the salt bridge electrode so that electrolyte measurements are inaccurate.
The present invention seeks to overcome these drawbacks and to provide a salt bridge element which is relatively simple to locate in a flow cell in self-alignment.